Bicycles which are known at the present time, incorporating a change-speed gear arrangement, either have a hub-type gear arrangement or a chain-type gear arrangement, often referred to as a derailleur gear arrangement because the drive chain is shifted or `derailed` from one sprocket to another, on a sprocket cluster having a multiplicity of sprockets.
The hub-type gear arrangement suffers from the disadvantage that the number of available gear ratios is greatly restricted. Although with increasing design development of such gear arrangements, it is now possible to design hub-type gear arrangements with up to seven gear ratios or shift stages, very complicated design configurations are then required in such an arrangement and the components which make up the assembly must accordingly be very small. A hub-type gear arrangement must more specifically always operate on the basis of the principle of a planetary transmission so that the same direction of rotation as between the chain sprocket and the wheel hub is maintained.
Hitherto the only possible way of providing a substantially larger number of shift stages or gear ratios has been the chain shift gear arrangement or derailleur gear. However such arrangements suffer from the disadvantage that, in spite of all the endeavours that have been made in terms of design configuration, even nowadays the chain can still easily jump off the chain sprockets, in particular when shifting from one gear to another. In addition although in theory the derailleur gear arrangement can provide a given number of gear ratios which is determined by the number of rear sprockets and the number of front chainwheels, it is in fact not possible to make use of all those theoretically available gear ratios as in same extreme situations the chain would then run at an excessively acutely extending line and that would inevitably result in the chain jumping off the sprockets or other major problems such as noise and lack of smoothness in transmission of the drive force by way of the chain, and severe chain wear. In addition the chain requires regular care, in the form of lubrication, and at the same time represents a possible source of fouling and damage in regard to the clothing of the cyclist.